found this on another site...this guy says he's pushing 420 HP on this 04 4.8....must be a factory freak

e-fans...balancer/pulley...superchips on kill...jba shorties with bullets, 2 1/2" duals...msd wires...k&N cold air system...01 ls6 cam with springs & titanium retainers...comp pushrods...crower ultra lite lifters...heads stock with .025 milled, mild bowl job paying attention to the valve bosses and the area on the intake behind the bosses, super polish on the exhaust with mild bowl job...i used some titanium intakes but you dont have too....the superchips is right on the edge with the timing so use good gas.